Europa from Voyager
Jupiter’s ice moon Europa is one of four main moons of the huge gas giant Jupiter, and ever since scientists realised that this place hides a salty ocean beneath its surface, well that made Europa pretty much top of the list when it comes to searching out any potential alien critters hiding out in the solar system. Europa’s subsurface ocean is no insignificant amount of water either, there’s a lot of it, more of the wet stuff exists on Europa actually than all of Earth’s oceans put together. That’s pretty amazing for a globe only about the same size as Earth’s moon, but this water exists because of the influence of Jupiter’s immense gravity flexing the frozen moon and warming it as it orbits around the giant planet. This alien ocean is known to lie deep though, very deep, up to 160 kilometres locked away far below the frigid ice crust that is exposed to the deep freeze of space. So scientists have always dreamt of sending a probe to this world of Jupiter’s to land on its surface, and burrow down to the ocean far below to find out what is or isn’t there. But there’s literally tens of miles of ice on Europa standing in the way of any space probe that wants to get at the watery goods.
But now scientists have landed some very interesting results about Europa from a spacecraft that doesn’t even exist any more. The very successful Nasa Galileo Spacecraft that was launched to Jupiter in the late eighties, collected huge amounts of data during its 34 orbits, enough for decades worth of study. This spacecraft’s mission was eventually ended on 21st of September 2003 when it was deliberately sent on a death mission into the storm clouds of Jupiter to be crushed into nothing in its colossal gravity. This was done to protect the pristine world of Europa from any contamination.
A large body of water exists just beneath the surface equal to North America’s Great Lakes
Scientists have now discovered that Europa might be an even cosier place for life than previously thought. A large body of water much closer to the surface has been found from Galileo’s science results, in effect a lake just below the surface with about the same amount of water as the Great Lakes of North America. Saturn’s moon Titan is known to be the only place other than Earth where liquid exists on the surface in the form of lakes, but Europa is now nearly there but not quite, there’s no liquid water actually on the surface of Europa but it’s not that far below it. Nasa scientists know that the ice moves about on Europa, there are areas clearly visible called chaos terrain where icebergs are in motion, it’s a jumbled mass of ice rafts, blocks, and cracks…chaos really!
An area such as this exists above the newly found large body of water, this warmer salty water wells up from just below the surface moving icebergs around, cracking the ice crust, and very importantly creating a cycle. This cycle is the water that moves between the surface of Europa, to the lake below, and ultimately to the ocean deeper still. There is actually communication between the subsurface water and the ice surface, very important for the chances of life. It was thought that if Europa’s ocean was locked away 100 miles below the crust there would be no transfer of material between that ocean and the surface, then that would be bad for the possibility of life, although not impossible. But it’s now known that is not the case any more, if there’s biology going on then it’s a dynamic cycle of nutrient transfer between the ocean and the moon’s surface. That original idea of a completely solid 100 mile thick ice barrier overlying the main ocean is no longer correct.
Scientists believe other “Great lakes” of Europa probably exist beneath these chaos terrains. This new discovery of water near the surface now means any proposed mission to get at Europa’s potential habitats for extraterrestrial life are now less of an engineering challenge, although it’s still no walk in the park.
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